Network communication standards are widely used in computer networks to communicate information between computers and other electronic devices. One widely-used standard is Ethernet, including several different standards for different network bandwidths. One Ethernet standard is 10GBASE-T, allowing 10 gigabit/second connections over unshielded or shielded twisted pair cables, over distances up to 100 meters. There is a desire to have more energy-efficient Ethernet standards for all flavors of Ethernet including 10GBASE-T.
To reduce the power consumption of 10GBASE-T transceivers, proposals have been suggested for a low-power idle (LPI) mode that consumes less power. The LPI mode turns off most of the component blocks of a transceiver during periods of inactivity, and periodically turns on transceiver blocks for a short period to maintain particular components of transceivers on the network and to determine whether LPI mode should be exited and transceiver power turned on for active operation.
For example, FIG. 1 shows a graph 2 illustrating a proposed power scheme for a low-power idle mode in 10GBase-T. The transceiver blocks consume full power in the nominal mode of 10G operation during active operation. When the transceiver becomes inactive due to having no data to transmit at time T1, the power for the transceiver is turned off to a minimal level and the transceiver enters low-power idle mode. However, the power is periodically turned back on during low-power idle mode for two purposes: 1) to maintain the proper states of near-end and far-end receivers in the transceiver and connected transceivers, such as updating filters and maintaining timing lock, so that the transceivers can return to active operation more quickly, and 2) to be able to detect reception of a transition bit sent by a far-end transceiver, the transition bit requesting the local transceiver to transition back to the nominal full-power mode of 10G operation. Thus, after a predetermined number of time intervals (i.e., frames), power is brought back on at time T2 and kept on for a predetermined number of frames, and is then returned to its minimal level at time T3 for a number of frames. The interval of minimal power level can be considered a quiet interval N during which power is off, followed by a refresh interval M during which power is temporarily brought back on (the interval N+M being the refresh period). This sequence of quiet and refresh intervals is repeated until a transition bit is detected during a refresh interval, such as at time T4, at which point the power is maintained at the fully-on level and the transceiver is transitioned back to full power mode.
The average power consumed during the low-power idle mode is much lower than in the nominal full power mode of 10G operation. For example, the power savings is approximately proportional to the duty cycle, which is N/(N+M). To provide a fast transition back to the nominal full power mode, the desired transition time is small. The transition time from LPI mode back to the nominal full power mode is approximately equal to the refresh period, N+M.
Despite the advantages of the existing low-power idle mode, there are some tradeoffs which decrease its effectiveness. For example, the receivers in the powered-down local and far-end transceivers require filter adaptation to train and maintain filter states (e.g., for filters such as Near End Crosstalk (NEXT) cancellers, Far End Crosstalk (FEXT) cancellers, equalizers and echo cancellers), as well as timing updates to maintain a timing lock with the Master transceiver. This adaptation and timing is strongly coupled with the transition time and power savings, because long and frequent adaptation intervals are desirable to allow accurate filter adaptation and timing lock, yet short and infrequent adaptation intervals are desirable to reduce power consumption. Furthermore, short quiet intervals are desirable to allow a short transition time, yet long quiet intervals are desirable to reduce power consumption. These factors create conflicts in design goals. However, existing inflexible low-power idle mode implementations do not allow flexibility in accommodating different receiver requirements, such as different durations and frequencies required for filter adaptation and timing lock. Furthermore, existing low-power idle mode implementations may create non-stationary noise (e.g. crosstalk from too-close cables) due to the frequent switching on and off of power during the low-power mode, which degrades the performance of adjacent ports of a transceiver. In addition, existing low-power idle mode implementations do not specify additional techniques which can provide additional power savings for a transceiver in low-power idle mode.
Accordingly, what is needed are systems and methods that provide low-power idle modes that permit greater flexibility in receiver architecture within desired restrictions of power savings and transition time, provide greater efficiency in the use of refresh periods, provide reduced noise, and/or provide additional power savings.